1. Technical Field
The present invention relates to a microlens array substrate, an electro-optic device, and an electronic apparatus.
2. Related Art
An electro-optic device has been known that is provided with an electro-optic material (for example, liquid crystal and the like) between an element substrate and an opposite substrate. A liquid crystal device that is used as a liquid crystal light valve of a projector is an example of the electro-optic device. An attempt has been made to realize high light utilization efficiency for such a liquid crystal device.
For example, a configuration has been known in which at least one of the element substrate and the opposite substrate of the liquid crystal device is the microlens array substrate and light blocked by a light blocking layer among light incident on the liquid crystal device is condensed by the microlens so as to make the light incident on an opening region of a pixel. The configuration accomplishes a substantial improvement in an aperture rate of the liquid crystal device. The microlens array substrate includes a substrate made of quartz, inorganic glass, or the like, on which plural concave portions are formed on the surface, and a lens layer having a different refractive index from that of the substrate, which is formed so as to fill a concave portion covering the substrate (for example, refer to JP-A-2004-4745).
On the microlens array substrate disclosed in JP-A-2004-4745, the concave portion (recess) of the substrate is filled with a lens layer made of an adhesive having a high refractive index. When isotropic etching processing is performed on the substrate through a mask layer to form the concave portion, unnecessary substances generated by the reaction between the substrate and the etching liquid are accumulated on the substrate surface of the concave portion. Therefore, the unnecessary substances accumulated in the concave portion cover the substrate surface and hinder circulation of the etching liquid. Thus, while the edge portion of the concave portion is formed almost spherically, the center portion of the concave portion is formed almost flat, and etching stops in this state.
However, when the edge portion of the microlens (concave portion) is formed almost spherically as described in JP-A-2004-4745, the angle between the tangent of the edge portion and the surface of the substrate in the cross section passing through the center portion of the concave portion is nearly 90°. Therefore, light incident on the edge portion of the microlens (concave portion) along a normal direction of the surface of the substrate is refracted significantly with respect to the normal direction due to a difference between the refractive index of the substrate and the refractive index of the lens layer. As a result, when the angle of the light refracted in the edge portion of the microlens is larger than an angle at which light can be incident on a region of a corresponding pixel, the light is blocked by a light blocking layer arranged between the pixel and an adjacent pixel. Then, the light utilization efficiency is not improved as desired and there is a concern of a display of the liquid crystal device becoming dark. In addition, when the angle of the light refracted in the edge portion of the microlens is increased, the angle of the light passing through the microlens and being incident on a liquid crystal layer with respect to an orientation direction of the liquid crystal varies significantly at the center portion and the edge portion, and thus, there is a concern of causing deterioration of contrast in the liquid crystal device.